My last bugfix added -Os on the command line, which unfortunately causeda build regression on powerpc in some configurations.

I've done some more analysis of the original problem and found slightlydifferent workaround that avoids this regression and also results inbetter performance on gcc-7.0: -fcode-hoisting is an optimization stepthat got added in gcc-7 and that for all gcc-7 versions causes worseperformance.

This disables -fcode-hoisting on all compilers that understand the option.For gcc-7.1 and 7.2 I found the same performance as my previous patch(using -Os), in gcc-7.0 it was even better. On gcc-8 I could see nochange in performance from this patch. In theory, code hoisting shouldnot be able make things better for the AES cipher, so leaving itdisabled for gcc-8 only serves to simplify the Makefile change.